Mining machine for mining material from the entire face



June 23, 1970 E BENNETT ET AL 3,516,712

MINING MACHINE FOR MINING MATERIAL FROM THE ENTTllI-I FACE Filed Aug.19, 1968 4 Sheets-Sheet I N Q. V |I I III m I l l I :I NI II N I I m a Im J a a 9 I I I IIII: I

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v BYDMIIIW ATTORNEY 4 shun-5 51mm J. E. BENNETT ET AL June 23, 1970MINING MACHINE FOR MINING MATERIAL. FROM THE mum-1 mm:

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MINING MACHINE FOR MINING MATERIAL FROM THE ENTIRE FACE Filed Aug. 19,1968 4 Shoots-$huut 3 /N\/ENTO/?5; JOHN E.BENNE'IT FAY'E.MUNGEQ,

A" TOP/YEY June 23, 1970 J. E. BENNETT ET AL 3,516,712

MINING MACHINE FOR MINING MATERIAL FROM THE ENTIRE PAGE 4 Sheets-Sheet 4Filed Aug. 19, 1968 mNG N NN E VBM u fi @ME A M W VFD :opposite ribsUnited States Patent 3,516,712 MINING MACHINE FOR MINING MATERIAL FROMTHE ENTIRE FACE John E. Bennett, Columbus, and Fay E. Munger, UpperArlington, Ohio, assignors to Jeffrey Gallon Inc., a corporation of OhioFiled Aug. 19, 1968, Ser. No. 753,460 Int. Cl. E21c 27/24 US. Cl. 2996411 Claims ABSTRACT OF THE DISCLOSURE A mining machine with a transverserotary mining head to mine material from the entire area of the mineface by traversing the mining head through the, mine face, and whichproduces a curved or arched form of the roof at each rib.

The instant invention relates to mining machines for mining materialfrom the entire area of the mine face ahead of the mining machine.

In typical underground mining operations the material is mined from themine face by a cutting and breaking action. The mining machine advancesforwardly in the direction of the mine face to penetrate the face forthe cutting and breaking action. It is a fundamental objective to minethe material at the highest rate, which is reflected in the rate ofadvance of the mining machine. The higher the rate that the material isremoved from the mine face, the higher is the rate of advance of themining machine.

The mining machine customarily has a mining head at its forward end,which is sumped into the mine face and mines the material by cutting andbreaking. After the mining head is operated over the entire face area,the mining machine is advanced to again sump the mining head into themine face and the operationis repeated. It is desired that'thesuccessive steps of advance'be performed on a continuing basis, and therate at which the material is mined from the mine face determines therate at which the mining machine can be advanced for the successivesteps of miningthe material.

Another factor that affects the rate of advance of the mining machine isthat of roof control. It is a serious problem in underground miningoperations that as the mine face is advanced there is produced anexposed roof which was formerly supported by the material that has beenmined from under the roof. This gives rise to the possibility of rooffalls. Due to the nature of the geological strata, roof falls mayinvolve tons of'material, such as slate and rock, with the potential tocause personal injury and damage to the equipment. Therefore, great careis taken in underground mining operations to control the roof, with thepurpose to avoid falls, and this is even subject to governmentregulations having the force of law.

In mining operations the roof may be controlled by the use of posts orprops set between the floor and the roof as a substitute for the minedmaterial, to provide vertical support. Another form of roof control istimbering in which timbers are set vertically, usually at the andanother timber is laid across the tops of the upright timbersimmediately below and bearing up against the roof. Wedges are driven into force the cross timber against the roof in close contact to providevertical support. Still another form of roof control is by roof boltingin which bolts with long shanks, of the order of three feet to four feetin length, are driven in above the roof and a plate is laid against theroof and held in place by a nut that is turned on the bolt. Roof boltingis advantageous because it permits "ice greater flexibility inthe'placement of the roof supports (than is the case with timbers, theroof bolts have considerably less bulk than the timbers, and thereforeare easier to handle and do not occupy as much space as the timbers. Theprinciple of roof bolting is to tie the strata immediately above theroof to more secure strata, thereby supporting the lower strata fromhigher firmer strata.

Any of the roof control systems are non-productive in nature, in thatthey do not directly produce mined material. The roof control proceduresinterrupt the actual mining operation, since the mining machine isstopped to permit roof supports to be installed. It is a limiting factorthat the mining machine may not advance beyond a given distance underunsupported roof. Therefore, when the mining machine is advanced throughthis distance it must be stopped until roof supports are installed. Thenthe mining machine may resume its advance through the given distance, atwhich time there is another shutdown while the roof supports are placed.The distance that a mining machine may advance under an unsupported roofis usually relatively short, so that the production of the machine ismaterially affected by the necessary interruptions to install roofsupports, and it is not possible to realize the full production capacityof the machine.

The mine face presents a face area Which is bounded by the floor at thebottom, the roof at the top, and the ribs at the opposite sides, fromwhich the material is mined. It is desired to remove the greatest volumeof material from the mine face. Consonant with this objective thecorners of the mine face would be cut square, to mine all the materialbetween the boundaries of the floor, roof and opposite ribs. However,the square cut corners at the roof produce a poor condition from thestandpoint of roof control. The roof control is improved in the case ofboring machines which have large circular boring heads that advance intothe mine face in the direction of the axes of the circular boring heads.The boring heads produce an arcuate configuration of the roof at eachrib, which is a portion of the circle of the boring head. The physicaleffect of such arcuate configuration of the roof at each rib is similarto that in an arch in which the arch is self-supporting. However, theroof that is produced by the boring machines is not totallyself-supporting, but there is a large measure of additional support forthe roof stemming from the arched or curved configuration at the ribs.With this added measure of roof support it is possible to advance themining machine through greater distances than would otherwise be thecase before the machine is stopped for the installation of roofsupports. This permits uninterrupted operation of the mining machineduring longer "periods of time, and materially improves the efficiencyof the mining operation.

The boring type mining machine characteristically has a mining headwhich covers the entire face area. The mining head includes the circularboring heads and trimming cutting chains or trimming cutting bars whichspan the distance between the circular boring heads where the latter donot overlap. These trimming cutting chains or cutter bars provide a flatfloor surface for the advance of the mining machine.

In another type of mining machine there is a rotary mining head which isconsiderably smaller than the area of the mine face from which thematerial is mined. The mode of operation is to sump the mining head intothe material of the mine face, and then to traverse the mining headthrough the material to cut and break the material out of the mine face,and in this manner to cover the entire area of the mine face between theroof, floor and the opposite ribs. Such a mining machine is illustratedin the patent to James Kilbourne, Pat. No. 3,305,273, Feb. 21, 1967, forMining Apparatus Supporting and Driving Construction. The rotary mininghead of the patent has a plurality of cutting bits disposed in acylindrical form, which in the course of operating the mining machineproduce square corners at the junctions of the roof with the oppositeribs. While this form of cutting head is effective to remove thegreatest volume of material from the entire face area, it is not mostsatisfactory for roof control.

Accordingly, it is an object of this invention to provide a miningmachine with a transverse rotary mining head, which produces a curvedroof at each rib to improve the roof control.

It is another object of the invention to provide a mining machine with atransverse rotary mining head to mine material from the entire mine faceby traversing the face and to form the roof with a curved or arched format each rib.

It is a further object of the invention to provide an improved miningmachine in which the mining head mines material from the entire mineface and produces a curved or arched form of the roof and floor at eachrib with a substantially flat intermediate part of the roof and floor.

It is also an object of the invention to provide an improved transverserotary mining head for traversing the mine face to mine material fromthe entire area of the mine face, in which each of the opposite ends ofthe mining head has a hemi-ovate form to form the roof with a curved orarched portion at each rib.

Other objects of the invention will appear hereinafter, the novelfeatures and combinations being set forth in the appended claims.

In the drawings:

FIG. 1 is a side elevation of a mining machine in accordance with theinvention;

FIG. 2. is a plan view of the mining machine;

FIG. 3 is a front elevation view of the rotary mining head with anoutline of the mine face area in which the material is mined;

FIG. 4 is an end elevation view of the rotary mining head; and

FIG. 5 is a section view of one end of the rotary mining head.

Referring to the drawings, there is illustrated in FIGS. 1 and 2 amining machine in accordance with the invention, supported on endlesstraction treads 11, 12 at opposite sides by which the machine ispropelled. At the forward end of the mining machine 10 there is a rotarymining head 13, on a transverse axis, to be advanced or sumped into themine face 14, and traversed through the material of the mine face, themine material from the entire face area by a cutting and breakingaction. The mining head 13 is supported on the forward end of a boom 15by which it may be raised to the roof 16, sumped into the material ofthe mine face 14, and traversed through the material downwardly to thefloor 16. The mining head 13 extends transversely between the oppositeribs 18, 19, and the latter define the side boundaries of the face areathat is mined by the mining head 13. The mining head 13 is supported onthe boom 15 at the forward end of the mining machine 10, for rotation ofthe mining head 13 about its transversely disposed axis.

The boom 15 is connected to the mining machine main frame on transversepivots 21, 22 on which the boom 15 is swung upwardly and downwardly bycylinders 23, 24, connected between the main frame 20 and the boom 15.

The mining machine 10 is powered by motors 25, 26 on opposite sides ofthe boom 15. Driving connections 27, 28 extend forwardly from motors 25,26, respectively, to transmissions 29, 30, at opposite sides of the boom15, from which the mining head 13 is driven. Pat. No.

4 3,305,273 illustrates in detail a form of the driving connections andtransmissions by which the mining head 13 may be driven, in which thepower of both motors 25, 26 is delivered to the entire mining head 13.

The motors 25, 26 also provide power for driving traction treads 11, 12.Drive connections 31, 32 extend rearwardly from motors 25, 26,respectively, to transmissions 33, 34 at opposite sides of the mainframe 20 for delivering the drive to the traction treads 11, 12.

In the mining operation the material cut and broken out of the mine face14 falls to the floor 17. There is a gathering head 35 at the front ofthe mining machine 10, below the boom 15. The gathering head 35 has anapron or deck 36 with its leading edge at the floor 17. Gathering arms37, 38 at opposite sides of the gathering head 35 operate with anoscillating motion to reach doWn and to sweep the material into aconveyor 39 which extends longitudinally through the mining machine 10from the gathering head 35 to the discharge boom 40 at the rear end ofthe mining machine 10. The conveyor 39 moves the mined material from theforward end of mining machine 10 to its rear end at which it isdischarged to conveying apparatus for removing the mined material fromthe mining place. The gathering arms 37, 38 are powered by the motors25, 26. Driving connections 41, 42 extend forwardly from transmissions33, 34, respectively, to gathering head transmissions 43, 44, from whichthe gathering arms 37, 38 are driven.

In FIG. 3 there is a front elevation view of the rotary mining head 13.There is an intermediate section of the mining head 13 with spiralflights 51, 52 at diamet rically opposite positions, and additionalspiral flights 53, 54. Several cutting bit holders 55, 55 are secured atspaced positions on the peripheries of the spiral flights 51, 52, 53,54. A cutting bit 56 is releasably secured in each holder 55. Thecutting bits 56 and their holders 55 are disposed at spaced positions inthe circumferential direction and in the axial direction of the mininghead 13, such that when the mining head 13 rotates, the cutting bits'56, 56 sequentially engage the material of the mine face at severalpositions across the mine face.

At the left side of the intermediate section 50 of the mining head 13,as viewed in FIG. 3, there is a cutting chain 58 extending around a gearcase 57 at the forward end of the boom 15, that may be constructed inthe manner of Pat. No. 3,305,273, and the gear case 57 forms a supportfor the mining head 13 on the boom 15 at the forward end of the miningmachine. Such gear case supports 57 for the mining head 13 are eachlocated at a position that is a substantial distance inward from theopposite ends or lateral extremities of the mining head 13 so that thereis a free length of the mining head 13 that extends transverselyoutwardly in opposite directions from the gear case supports 57 alongthe transverse axis of the mining head 13. The path of cutting chain 58is coincident with a major part of the circumference of the mining head13, as best seen in FIG. 4. The chain 58 has a plurality of links 59, 59with connecting links 60, 60, and articulated connections including pins61, 61. The pins 61, 61 project from the opposite sides of the chain 58to be engaged by a sprocket 62 on the intermediate mining head section50 at one side of the chain 58, and another sprocket 63 at the otherside of the cutting chain 58, which is secured to the outer mining headsection 65. The sprockets 62, 63 rotate with the mining head 13 and byengagement with the outer ends of pins 61, 61 of the cutting chain 58drive the latter concurrently with the rotation of the mining head 13,which may be generally in the same manner as in Pat. No. 3.305,273.

A plurality of cutting bit holders 55 are secured to the links 59, ofcutting chain 58 at spaced positions along and across the latter toprovide a pattern of cutting bits 56, 56 in which they sequentiallyengage the material of the mine face 14 at spaced positions across theface,

as the cutting chain 58 is moved by rotation of the mining head 13.

The mining head 13 has an outer mining head section 65 at the left side,as viewed in FIG. 3, outboard of the cutting chain 58. Spiral flights66, 67 are wound on one part of the mining head section 65 atdiametrically opposite positions, and spiral flights 68, 69 are Wound onanother part of the mining head section 65 as continuations of thespiral flights 66, 67, respectively. A plurality of cutting bit holders55 with their cutting bits 56, are secured to the outer mining headsection 65 on the spiral flights 66, 67, 68, 69 at circumferentially andaxially spaced positions to sequentially engage the material of the mineface 14 at spaced positions across the latter during rotation of themining head 13.

Beyond the outer mining head section 65 there is an end mining headsection 70 as an axial extension of section 65. End section 70 isconnected to section 65 by a telescoping cylinder part 71 that may beextended and retracted relatively to section 65. The inner portion ofthe end section 70 in the area of telescoping cylinder part 71 hasspiral flights 72, 73 wound at diametrically opposite positions ascontinuations of spiral flights 68, 69, respectively, when end section70 is extended, as illus trated in FIG. 3. Several cutting bit holders55 and their bits 56 are secured at spaced positions on spiral flights72, 73, to sequentially engage the material of the mine face 14 atspaced positions across the latter. Beyond the spiral flights 72, 73,there is a collar 74 and an end cap 75 which are of successively lesserdiameters towards the outer end of the end section 70. A plurality ofcutting bit holders 55 and their hits 56 are secured to the collar 74and to the end cap 75 at spaced positions in the circumferential andaxial directions to sequentially engage the material of the mine face 14at spaced positions across the latter. The disposition of the cuttingbits 56 is best seen in FIGS. 3 and 4.

At the right side of the intermediate mining head section 50 there isanother cutting chain 58' like the cutting chain 58, but oppositelydisposed, and such cutting chain 58' and its parts are identified by thesame reference numerals, with the addition of a prime The right side ofthe mining head 13, as seen in FIG. 3, is the same as the left side, butthe elements are oppositely disposed. The elements of the right side ofthe mining head 13 are identified by the same reference numerals asapplied to the elements at the left side with the addition of a prime toeach reference numeral, and the description of the left side of themining head 13 applies also to the right side of the mining head.

The cutting bits 56, 56 on the intermediate mining head section 50 andon the outer mining head sections 65, 65 are all at the same radius, andin rotating the mining head 13 these cutting bits 56, 56 move in theform of a cylinder. Likewise, the cutting bits 56, 56 on the cuttingchains 58, 58 are disposed at the same radius so that they also move inthe same cylindrical form in the portion of their paths which coincidewith the mining head 13. These cutting bits 56, 56 moving in thecylindrical form, develop a flat intermediate surface 78 on the roof 16and a flat intermediate surface 79 on the floor 17. Beyond the outermining head sections 65, 65', the cutting bits '56, 56 which are on theend mining head sections 70, 70', are at positions of decreasing radialdistances towards the outer end of the mining head 13. In the rotationof the mining head 13, the cutting bits 56, 56 on the end mining headsections 70, 70' move in a hemi-ovate form and produce curved or archedsurfaces 80, 81 on the roof 16 downwardly to the rib 18 and to the rib'19, respectively. Similarly, the floor 17 is formed with a curvedsurface 82 up to the rib 18 and a curved surface 83 up to the rib 19.However, the flat intermediate surface 79 on the floor 17 is ofsuflicient width to accommodate the opposite traction treads 11, 12, asseen in FIG. 3, for movement of the mining machine 10 on a flat part ofthe floor 17.

In FIG. 3 the total cutting profile of the mining head 13 is illustratedby the phantom perimetal line 85. The profile line illustrates the equalradial distances of the cutting bits 56, 56 of the intermediate mininghead section 50, of the outer mining head sections 65, 65', and of thecutting chains 58, 58, and the decreasing radial distances of thecutting bits 56, 56 on the end mining head sections 70, 70', which formthe hemi-ovate end sections of the mining head 13. Such hemi-ovate endsections of the mining head 13 are formed along the free lengths of themining head 13 extending from adjacent to the respective ribs 18, 19transversely inwardly toward the supports 57 of the mining head 13 onthe forward end of the boom 15. At each extreme end or lateral extremityof the mining head 13, the cutting bits 56, 56 are in a crowndisposition, as best seen in FIGS. 3 and 4, and provide flattened endsof the opposite hemi-ovate sections of the mining head 13, to cut theribs 18, 19.

Referring to FIG. 5, there is'a shaft 87 extending axially through themining head 13. The end mining head section 70 has its telescopingcylinder part 71 slidably mounted on the shaft 87 with a key 88 .in akeyway 89. A slide collar 90 issecured to the outer end of the shaft 87,and a mating inner cylinder 91 is slidably engaged with the slide collar90 in sealed engagement. A bore 92 extends through the shaft 87 to theinner cylinder 91. Hydraulic fluid is delivered through the bore 92 intothe inner cylinder 91 to move the telescoping cylinder part 7-1 and theend mining head section 70 outwardly relatively to the shaft 87.

A coil spring 93 is disposed between the outer mining head section 65and the telescoping cylinder part 71. A ring 94 is secured to the outermining head section 65 abutting one end of spring 93, and a ring 95 issecured to the inner end of the telescoping cylinder part 71 abuttingthe other end of spring 93. In the extended position of the end mininghead section 70, as seen in FIG. 5, the spring 93 is compressed betweenthe rings 94, 95, and the end mining head section 70 is held in itsextended position by hydraulic fluid trapped within the inner cylinder91. The end mining head section 70 is retracted by release of thehydraulic fluid from the inner cylinder 91, and the force of the spring93 between rings 94, 95 withdraws the telescoping cylinder part alongthe shaft 87 and within the outer mining head section 65. Thetelescoping ends of the mining head 13 establish the maximum width ofcut between ribs 18, 19, since the crown ends of the mining head 13 abutribs 18, 19. The opposite mining head end sections 70, 70 are retractedto provide clearance at the ribs 18, 19 for moving the mining machine 10at other times than during the actual mining operation. During themining operation the mining head .13 is driven, and when advanced intothe mine face 14 it cuts its own clearance.

As illustrated herein, and particularly with reference to FIGS. 1 and 4,the mining head 13 is rotated in the clockwise direction so that thecutting bits 56, 56 engage the material in the mine face 14 in adescending direction. As viewed in FIG. 3, the cutting bits 56, 56 moveddownwardly from top to bottom of the profile line 85. The removal of thematerial from the mine face 14 1s a cutting and breaking action in whichthe cutting bits 56, 56 cut into the material, and concurrently, thecutting bits along with the several spiral flights break the materialout of the mine face and it falls to the floor 17.

Initially, the boom 15 may be raised to place the cutting head 13 at thetop of the mine face 14 adjacent the roof 16. The mining machine 10 isadvanced on its traction treads 11, 12 to sump the rotating mining head13 into the material of the mine face. Then the boom 15 is lowered, asthe rotation of the mining head 13 is continued, to cut and break thematerial out of the mine 7 face 14 as the mining head 13 is traverseddownwardly through the mine face to the floor 17. This procedure is thenrepeated for another cut by raising the mining head 13 to the roof 16and sumping it into the mine face 14 for the next traverse through thematerial of the mine face 14.

In the mining operation the mining head 13 is effectively moved alongthe roof 16 so that the form of the roof 16 matches the form of themining head 13 illustrated by the profile line 85 in FIG. 3. Thus, theroof 16 is exposed and formed with the curved or arched surfaces 80, 81adjacent the ribs 18, 19, respectively. This improves the roof controlby providing substantial intrinsic support for the exposed roof, andpermits considerably greater advance of the mining machine before it isnecessary to stop and to interrupt the actual mining operation for theinstallation of roof supports. The mine floor 17 also is formed withcurved or arched surfaces 82, 83 at the ribs 18, 19, respectively, andan intermediate flat surface 79 to accommodate the traction treads 11,12 for movement of the mining machine 10.

Having thus described and shown an embodiment of the invention, what itis desired to secure by Letters Patent of the United States is:

1. A mining machine with a rotary mining head that is disposed at theforward end of the mining machine to cut and break material out of amine face in a face area that is bounded by the floor at the bottom ofthe face, by the roof at the top of the face, and by the ribs at theopposite sides of the face, means to advance said mining head into thematerial of the mine face, a boom on the mining machine that extendsforwardly, said boom in cluding supporting means for said mining head onthe boom at the forward end of said mining machine for the mining headto meet the mine face and to traverse said mining head through thematerial of the mine face in the face area between the floor and theroof, said mining head being disposed transversely across the forwardend of said mining machine to rotate about one transverse axis, saidsupporting means for said mining head on said boom being located at aposition that is a substantial distance inward from the opposite ends ofthe mining head so that there is a free length of the mining head thatextends transversely outwardly in opposite directions from the mininghead supporting means along said one axis, Said mining head being atleast as wide as the width of the remainder of said mining machinebehind the mining head in order to cut the opposite ribs with sufficientdistance between the ribs for movement of the mining machine between theribs, each said free length of said mining head on opposite sides ofsaid mining head supporting means having a substantially hemi-ovate formalong the free length of the mining head extending from adjacent to therespective rib transversely inwardly toward said supporting means toproduce an arched roof that arches downwardly to the rib at each sideand to produce an arched floor that arches upwardly to the rib at eachside. 7 2. A mining machine as recited in claim 1 in which said mininghead includes means to extend and to re tract a portion of said freelength of the mining head including the hemi-ovate part of the mininghead in the transverse direction in order to increase and to decreasethe transverse width of the mining head between the opposite ribs.

3. A mining machine as recited in claim 1 in which said mining head hasa substantially cylindrical form between the opposite hemi-ovatesections of the free lengths of the mining head in order to cut asubstantially flat roof and floor between the opposite arched roof andfloor portions, respectively.

4. A mining machine as recited in claim 1 in which said oppositehemi-ovate sections of the free lengths of said mining head are eachterminated with a flat crown at the rib which cuts the material of therib.

5. A mining machine as recited in claim 1, including spiral flights onthe said mining head directed to feed mined material in toward thecenter of the mining machine, and cutting bits being mounted on saidspiral flights to engage the material of the mine face.

6. A mining machine with a mining head that is disposed at the forwardend of the mining machine to cut and break material out of a mine facein a face area that is bounded by the roof at the top of the face, bythe floor at the bottom of the face, and by the ribs at the oppositesides of the face, said mining head being disposed transversely acrossthe forward end of said mining machine and extending in a transversedirection, supporting means for said mining head that is disposed asubstantial distance inward from the opposite ends of the mining head toprovide a free length of the mining head at each side of said supportingmeans that extends along said transverse direction, means to advancesaid mining head into the material of the mine face, means to traversesaid mining head through the material of the mine face in the face areabetween the floor and the roof, said mining head including opposite endsections of said free lengths of the mining head each of which has asubstantially hemi-ovate configuration extending inwardly from saidopposite ends of the mining head toward said supporting means to cut theroof and the opposite ribs and forming an arched roof that archesdownwardly to the rib at each side.

7. A mining machine as recited in claim 6, including a forwardlyextending boom for said supporting means, means in the mining machine tomove said boom upwardl and downwardly, and said mining head is mountedon the forward end of said boom to be traversed through the material ofthe mine face by movement of said boom.

8. A miningr'nachine as recited in claim 6, including a spiral flightwound around the mining head, cutting elements mounted on said spiralflight to sequentially enter the material of the mine face and thespiral flight moves the cut material inwardly towards the longitudinalcenterline of the mining machine.

9. A mining machine as recited in claim 6, in which said oppositehemi-ovate end sections of the free lengths of said mining head areextensible and retractable to adjust the transverse width of the mininghead between the opposite ribs.

10. A mining machine as recited in claim 6, in which said mining headincludes a cylindrical mining head section intermediate said oppositehemi-ovate end sections of the free lengths of said mining head, andsaid opposite hemi-ovate end sections form transverse continuations ofsaid cylindrical mining head section.

11. A mining machine as recited in claim 10, in which each of saidopposite hemi-ovate end sections of the free lengths of said mining headhas a substantially flat crown at the respective rib to cut the surfaceof the rib as the mining head is traversed through the material of themine face.

References Cited UNITED STATES PATENTS 720,841 2/1903 Pawel 299 X3,128,998 4/1964 Sibley 29989 X 3,305,273 2/ 1967 Kilbourne 29976 X3,318,638 5/1967 Kilbourne 29976 3,362,753 1/1968 Sibley 29976 X ERNESTR. PURSER, Primary Examiner US. Cl. X.R. 29976, 80, 87

